Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$112.54	4.223%	$117.2926	$117.29	$117.30	$117.30
Purchase #2	$197.76	5.646%	$208.9255	$208.93	$208.95	$208.90
Purchase #3	$113.65	8.385%	$123.1796	$123.18	$123.20	$123.20
Purchase #4	$174.48	12.383%	$196.0859	$196.09	$196.10	$196.10
Purchase #5	$227.86	5.797%	$241.069	$241.07	$241.05	$241.10
Purchase #6	$137.64	10.472%	$152.0537	$152.05	$152.05	$152.10
Purchase #7	$54.52	6.792%	$58.223	$58.22	$58.20	$58.20
7 purchase totals =	$1,018.45		$1,096.8293	$1,096.83	$1,096.85	$1,096.90